Experiments with Monopoles, Rings and Knots in Spinor Bose-Einstein Condensates

Abstract

Topological excitations are ubiquitous in nature, their charge being a naturally-quantized, conserved quantity that can exhibit particle-like behavior. Spinor Bose-Einstein condensates (BECs) are an exceptionally versatile system for the study and exploration of topological excitations. Between the spin-1 and spin-2 87Rb condensates there are seven possible broken-symmetry magnetic phases, with each one hosting unique opportunities for topological defects. We have created and observed several novel topological excitations in a spinor 87Rb BEC. In this dissertation I present and discuss three principal experimental findings: (1) The discovery of an Alice ring, or a half-quantum vortex ring, emerging from a monopole singularity in a nematic spin-1 BEC; (2) The first realization of a \u27t Hooft-Polyakov-type monopole in a nematic spin-2 BEC; and (3) The first realization of a knot in a nematic spin-2 BEC. This dissertation concludes with possible avenues for future research

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